1. Field of the Invention
This invention relates to tape media technology, and more specifically, to positioning within an optical tape recorder.
2. Description of the Related Art
Optical Tape Recording Systems are now built according to two generic types that involve either scanning across the tape media width (optical recording) or simple non-scanning means of recording data tracks in the long tape direction (linear recording). Various linear recording techniques have been proposed for recording multiple parallel tracks along the tape parallel to the tape edge. In these linear recording designs, the optical recording media can be pre-formatted and the system is designed to record and then playback recorded signals while following a previously written track mark.
Optical recording typically employs a sub-micron track width, and designs commonly necessitate a large number of closely spaced tracks. With tens of thousands of microscopic tracks per inch of media, pre-formatting of optical tape is a difficult and burdensome process. Pre-formatting optical media usually requires the fabrication of specialized equipment specifically designed for that purpose. Designing and building an optical media pre-formatter is often more difficult than producing the optical tape recorder itself. Due to the difficulty of implementing pre-formatted tracks on optical tape media, a system compatible with non-formatted media would be a preferred means of recording.
Earlier optical tracking systems deal with these problems regarding the reading of recorded signals by incorporating the use of a servo system that detects and follows the written track. Designing a practical optical tracking mechanism able to follow such dynamic motion is problematic (e.g., mechanical systems capable of a millimeter motion and frequencies of up to 10 KHz are difficult or impossible to implement). Systems have been designed that follow large motions at low frequencies, or that follow small motions at high frequencies. However, the desired servo system should follow essentially all amplitudes at essentially all frequencies and allow track following to within about 0.2 microns of the track center. The stacking of two servo systems, one on top of the other, (e.g., large amplitude and low frequency with small amplitude and high frequency) is possible but difficult.
In addition, another advantage of optical tape systems is that the small width of the written track enables many tracks to be placed on the same section of media providing high recording capacity, however new tracks must not overwrite previously written tracks. This may not create a problem with pre-recorded media, but for unrecorded media the transverse tape motion prohibits adjacent tracks from being closely spaced unless some design solution is implemented to allow this.
A method and apparatus for optical tracking in an edge-guided tape recorder is provided. In one embodiment, an optical tape guiding system for use in an optical tape drive which may write to optical tape is provided. The optical tape has a first edge and is disposed to be transported through the optical tape drive, and the optical tape exhibits transverse motion during transport through the optical tape drive. The system includes a curved edge guide disposed to maintain contact with the first edge of the optical tape during transport through the optical tape drive. The system may further include a mirror galvanometer disposed to direct a record beam of the optical tape system to the optical tape.